A. Field of the Invention
The present invention relates generally to machines and apparatus for precisely positioning an ultrasonic bonding tool or similar implement relative to a workpiece. More particularly, the invention relates to ultrasonic bonding machines of the type which have a micro-manipulator apparatus that includes a manipulator input mechanism that is mechanically coupled to an output follower mechanism and which is responsive to motions of a hand control knob of the manipulator input mechanism in positioning the tip of a wire bonding tool at precisely determinable locations relative to a microcircuit or similar workpiece, moving the tool tip into contact with the workpiece where the tool is energized by ultrasonic energy and/or heat and pressure to bond a wire to a site on the workpiece, and retracting the tool tip from the bond site after making a bond. Specifically, the invention relates to an improvement in micro-manipulators for ultrasonic bonding machines which includes an auxiliary micro-manipulator control apparatus that is mechanically coupleable to the input control member of a micro-manipulator. The auxiliary control apparatus includes a motion control mechanism which has a manually operable input control arm. Motions of a hand control knob at the end of the input control arm mechanically cause motions of the input control member and tool of the micro-manipulator, and since the control arm is spaced laterally away from the input control member, using the apparatus expands useable lateral work space below the bonding tool of the machine.
B. Description of Background Art
A large variety of scientific procedures, medical procedures and industrial processes require the use of a type of apparatus referred to generally as a micro-manipulator for precisely positioning of a tip of a tool or instrument relative to a small workpiece or other such object. For example, the manufacture of electronic components such as integrated microcircuits requires the use of a micro-manipulator-type apparatus, for the following reasons.
Integrated circuits are fabricated from thin slices of a semi-conducting material such as silicon, germaninan, gallium arsenide, or other III-V compounds, i.e., compounds of elements from columns three and five of the periodic table. The slices are cut into small squares or rectangles referred to as chips or dice, ranging in size from squares about 100 mil (0.100 inch) on a side to several hundred mils. Transistors, diodes, resistors and interconnecting circuit paths are formed on each chip or die by diffusing impurities into selected regions of the die to produce a desired electrical conductivity. Various conducting paths and insulated layers are then deposited on the chip.
After a semi-conductor chip or die has been fabricated as described above, it must be attached to a base or carrier. A lid is then sealed to the base to form a package or container which protects the delicate die from damage. Prior to attaching the lid to the carrier which supports the die, conductive pads which provide input and output conductive paths to the die must be electrically interconnected to more robust leads or terminals which extend outward from the carrier. These interconnections are customarily made using fine aluminum or gold wires. Wires are ultrasonically bonded or thermosonically welded to bonding sites, such as die pads and external leads by a bonding tool which has a tapered tip that is moved downwardly to press a wire against a bonding site. Ultrasonic energy, or a combination of heat and ultrasonic energy, is then applied momentarily to the tool to bond the wire to the bonding site. Since the connection pads of a microcircuit are extremely tiny and closely spaced, great precision is required in positioning the tip of the bonding tool relative to the microcircuit.
Responsive to the need for an apparatus capable of precisely positioning the tip of an ultrasonic transducer-type bonding tool to form wire bonds on microcircuit chips, the present inventor invented a micro-positioner apparatus which employs a novel pantograph-type manipulator input mechanism. That apparatus, which was disclosed in the present inventor's U.S. Pat. No. 3,474,685 and issued on Oct. 28, 1969, has proven to be highly effective in performing its intended functions, and wire bonding machines employing the novel design concepts including the pantograph mechanism disclosed in that patent are widely used throughout the electronics industry. However, the present inventor found that certain aspects of the micro-positioner disclosed in the U.S. Pat. No. 3,474,685 patent might be improved upon. For example, the allowable working fore-and-aft working space or throat depth of the ultrasonic tool tip would preferably be larger for certain bonding applications.
Also, the use of offset pivotable mountings for the transducer tool support plate would desirably be minimized, thereby minimizing the requirement for springs to counter balance unbalanced forces exerted in supporting the tool support plate by such offset mountings. Moreover, it would be desirable to have a micro-positioner apparatus in which various ultrasonic transducers and other bonding tool accessories such as wire spooling mechanisms, some of which might be substantially heavier than conveniently supportable by prior art micro-positioners, could be used. Such a need arises, for example, in bonding the heavier wires required for connection to certain electronic components such as wound coils and memory disk drive components. In response to the foregoing considerations, the present inventor disclosed a Micro-positioner For Ultrasonic Bonding, U.S. patent application Ser. No. 08/773,637 filed Dec. 24, 1996, now U.S. Pat. No. 5,871,136.
In that patent application the present inventor disclosed a micro-positioner apparatus which has a 4-bar parallelogram linkage that comprises a pantograph-like manipulator input mechanism, and a follower mechanism coupled to the manipulator input mechanism by a ball joint and supporting an ultrasonic transducer housing and bonding tool on a tool support plate. The tool support plate is longitudinal slidably mounted on a tool support guide plate, allowing fore and aft motion of the tool tip. The tool support guide plate is in turn pivotably supported by a yoke having a yaw pivot bearing which allows lateral motion of the tool tip. The yoke is in turn supported by a pitch pivot bearing having a laterally disposed horizontal pivot axis, thereby permitting pivotal motion in a vertical plane of the yoke, tool support plate, and tool tip. By a suitable choice of spacings between the pivot axes of the pantograph manipulator input mechanism, support bearings and ball joint, the tip of the bonding tool is caused to move in coordinate directions of a second coordinate system containing the tool tip in precisely scaled ratios of corresponding motions in a first coordinate system of a manually grasped and manipulated input control knob on the input manipulator mechanism. The input control knob is located at the front or outer end of a fore-and-aft disposed, elongated manipulator input control arm, the rear and of the arm being attached to the front end of a fore-and-aft disposed right-hand one of the four parallelogram linkage bars. The combination of a longitudinally slidable tool support plate with two pivot bearings orthogonal to each other and to the slide axis, provides a micropositioner apparatus which has both a rugged construction capable of supporting heavy loads on the tool support plate, and a substantial throat depth. In a preferred embodiment of the disclosed apparatus, the longitudinal slide axis of the tool tip, and the pivot axes of the pitch and yaw pivot bearings all intersect at a common point, thereby assuring completely orthogonal motions of the tool tip in three orthogonal coordinate directions that are precisely scaled fractions, e.g., ⅛ for lateral (X), and fore-and-aft (Y), and 1/3.75 for up and down (Z) motions.
In U.S. Pat. No. 6,164,514, the present inventor disclosed a micro-manipulator for ultrasonic bonding applications which included a 4-bar, parallelogram manipulator input mechanism and a tool holder follower mechanism which are both pendent from an overlying support structure, thereby affording a work space of potentially unlimited lateral extent below the apparatus. The large work space provides advantages over previously existing micro-manipulators, including a capability for accommodating large workpieces, which may optionally be supported on a conveyor belt located below the apparatus. Although the large lateral extent of the work space afforded by the micro-manipulator disclosed in U.S. Pat. No. 6,164,514 proved highly advantageous, full utilization of that space was hindered in certain applications, for the following reason. The micro-manipulator input mechanism disclosed in the '514 patent includes an input control arm which extends forward from the machine, the arm having at its outer or forward end a control knob which is grasped by an operator and moved in orthogonal directions to produce corresponding smaller motions of a bonding tool tip, in three orthogonal directions. When the control knob was moved downwardly sufficiently far, an operator's hand could inadvertently contact a workpiece which extended laterally sufficiently far from the bonding tool tip. A possible solution for the interference problem would be to increase the length of the input control arm sufficiently for the control knob to extend forward from the desired work space in front of the apparatus, thus avoiding contact of the control arm knob or operator's hand with the workpiece. However, increasing the length of the control arm would undesirably alter the kinematic scaling ratios of tool tip motions to input control knob motions. The present invention was conceived of to solve the above-described mechanical interference problem without altering existing scaling ratios between the control arm and tool tip of a micro-manipulator, thus expanding useable working space of the micro-manipulator.